Department of Chemistry, Graduate School of Science, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan.
Peptides. 2010 May;31(5):794-805. doi: 10.1016/j.peptides.2010.01.006. Epub 2010 Jan 28.
Although several low amphipathic peptides have been known to exhibit antimicrobial activity, their mode of action has not been completely elucidated. In this study, using designed low amphipathic peptides that retain different alpha-helical content and hydrophobicity, we attempted to investigate the mechanism of these properties. Calorimetric and thermodynamic analyses demonstrated that the peptides induce formation of two lipid domains in an anionic liposome at a high peptide-to-lipid ratio. On the other hand, even at a low peptide-to-lipid ratio, they caused minimal membrane damage, such as flip-flop of membrane lipids or leakage of calcein molecules from liposomes, and never translocated across membranes. Interaction energies between the peptides and anionic liposomes showed good correlation with antimicrobial activity for both Escherichia coli and Bacillus subtilis. We thus propose that the domain formation mechanism in which antimicrobial peptides exhibit activity solely by forming lipid domains without membrane damage is a major determinant of the antimicrobial activity of low amphipathic peptides. These peptides appear to stiffen the membrane such that it is deprived of the fluidity necessary for biological functions. We also showed that to construct the lipid domains, peptides need not form stable and cooperative structures. Rather, it is essential for peptides to only interact tightly with the membrane interface via strong electrostatic interactions, and slight differences in binding strength are invoked by differences in hydrophobicity. The peptides thus designed might pave the way for "clean" antimicrobial reagents that never cause release of membrane elements and efflux of their inner components.
尽管已经知道几种低两亲性肽具有抗菌活性，但它们的作用机制尚未完全阐明。在这项研究中，我们使用保留不同α-螺旋含量和疏水性的设计低两亲性肽，试图研究这些性质的机制。量热和热力学分析表明，这些肽在高肽-脂质比下诱导阴离子脂质体中形成两个脂质域。另一方面，即使在低肽-脂质比下，它们也会引起最小的膜损伤，例如膜脂的翻转或钙黄绿素分子从脂质体中的泄漏，并且从不跨膜转运。肽与阴离子脂质体之间的相互作用能与大肠杆菌和枯草芽孢杆菌的抗菌活性都有很好的相关性。因此，我们提出了这样的观点：抗菌肽通过仅形成脂质域而不破坏膜来发挥活性的域形成机制是低两亲性肽抗菌活性的主要决定因素。这些肽似乎使膜变硬，从而使其丧失了生物功能所需的流动性。我们还表明，为了构建脂质域，肽不需要形成稳定和协作的结构。相反，肽只需通过强静电相互作用与膜界面紧密相互作用，并且通过疏水性的差异来调用结合强度的微小差异是必不可少的。因此，设计这些肽可能为“清洁”的抗菌试剂铺平道路，这些试剂永远不会导致膜元件的释放和其内部成分的外排。
